What happens to a cell as it is placed in a hypertonic solution?

A hypertonic solution has a higher concentration of solute than the cell it surrounds. This means there’s more stuff (e.g., ions from salt) dissolved in it. This means the concentration of water in the solution is decreased. The more ions dissolved in a solution, the less of that solution is just pure water.
Because of osmosis, where water moves from an area with a high concentration of water to an area from a lower concentration of water, the hypertonic solution will draw water out of the cell, in order to try and equalise the concentration of water inside the cell and outside it. This means the cell will shrivel up!